1. Field of the Invention
The present invention is directed to a transfer printing station with an electrostatic transfer printing means for transferring a toner image generated on an electrographic intermediate carrier onto at least one recording medium in a transfer printing area of the transfer printing station, with guide elements arranged in the transfer printing area for guiding the recording medium close to the intermediate carrier during the transfer printing event, and with a contact pressure element arranged between the guide elements that presses the recording medium against the intermediate carrier during the transfer printing event.
2. Description of the Related Art
Such a transfer printing station is disclosed by U.S. Pat. No. 5,400,125. It employs a leaf-shaped blade as a contact pressure element, the edge thereof pressing the web-shaped recording medium against the electrographic intermediate carrier, a photoconductor drum. Although relatively good practical results have been capable of being achieved with this solution, a few disadvantages nonetheless derive. Thus, the blade-shaped contact pressure element is a wear part whose service life is relatively short and that requires frequent replacement. Since the blade edge of the contact pressure element rubs against the recording medium, considerable contamination due to toner abrasion and paper abrasion derives in the transfer printing area. When different web widths of the recording medium are employed, then a contact pressure element matched to this web width must be utilized. Due to the blade-shaped contact pressure element, moreover, irregularities in the electrostatic field derive in the transfer printing area; these irregularities can produce stripes in the print image.
Japanese Patent document discloses a transfer printing station with a contact pressure element in the transfer printing area. The contact pressure element is fashioned at a guide element, whereby the transfer printing station contains only a single guide element. The contact pressure element is fashioned a as contact pressure roller and has lateral supporting wheels that are supported on edge regions of an intermediate carrier that have no image-generating function. The recording medium is supplied with an edge close to a supporting wheel. The other supporting wheel has a larger diameter than the first-cited supporting wheel, as a result whereof a wedge-shaped gap forms between the surface of the contact pressure roller and the surface of the intermediate carrier. What is thereby achieved is that the contact pressure roller is not charged with toner material in the area of the enlarged gap.
German Patent document discloses an electrographic printer wherein two webs of a recording medium lying side-by-side are simultaneously printed. One of the webs can have already undergone a fixing process.